Erosion and exhumation of granitic blocks in La Pedriza del Manzanares, Spain. Historical evolution from relative dating

Abstract

La Pedriza del Manzanares is a granite landscape protected within the Sierra de Guadarrama National Park (Madrid, Spain). These granites create a landscape alternating fresh outcrops, regolith zones and numerous individual boulders that have been transported and partially buried by slope deposits. Erosion of the materials covering these boulders has allowed the identification of several levels of flared slopes and tafoni formed from successive episodes of soil stabilisation. By relating peak height from flared slopes and/or tafoni to the erosion rates for similar climatic areas, we estimated the required time for the formation of these morphologies. The method used provides an adequate tool for the relative dating of slopes in areas of similar geomorphology.